Open Baffle speakers

[atmasphere]

I have not mentioned a FR error.

I think I will bow out here as I have no idea what “cubic non-linearity” even means.

Yes, as I mentioned in my last post I realized you were not talking about FR.

Amplifiers tend to exhibit a 'quadratic non-linearity' if the circuit is single ended.

It will be cubic if the amplifier is entirely balanced/differential from input to output (this is because even ordered harmonics are cancelled, so distortion compounds less from stage to stage).

Amplifiers that have a single-ended input combined with a push-pull output have both non-linearities. Due to algebraic summing this kind of circuit will exhibit a bit more 5th harmonic.

Feedback suppresses the distortion of these non-linearities. But since too little feedback is used in 99% of amplifiers ever made, the kind of non-linearity that exists will say a lot about how the amplifier 'sounds'. This is simply because the differences you hear between amplifiers, their 'sonic signature' is really their distortion signature. Due to tipping points in the brain, it seems to pay more attention to tonality induced by distortion than it does actual FR errors- unless the FR error is too profound...

Unless you really want to dig into the math of how the amp makes distortion, this might be all you need to know. You can think of any amplifier as the amplifier block being perfect, but also there is a series non-linearity through which the signal must also go.

 

[Adi777]

Benchmark, Soulution i Purifi.

Soulution from Switzerland? Very expensive, but looking nice.

 

[Flaesh]

Hope someone we'll see such measurements

I think Erin can test simple any raw driver))

upd: measured Maggy https://audiosciencereview.com/forum/index.php?threads/open-baffle-speakers.39042/post-1382968

 

[Flaesh]

A dipole is the only radiator that is directional down to the lowest frequency

Let's consider plane travelling wave; can you calculate directivity index for this case?))..

 

[olegtern]

I think Erin can test simple any raw driver))

I even forgot what it was about

 

[Tim Link]

I have heard a few, and while they do "Seem" to offer a few key advantages or seem at least interesting sounding in some ways.....

I have found those that tend to champion them, are very defensive about them in general, and tend to skim over the disadvantages and often are not even totally aware of some of the downsides. Similar to how some Vinyl guys will skirt around built in issues with vinyl records.

When I mentioned "Baffle Peaking" on another forum, I got mostly crickets and told I was making up stuff or just bashing their baby speakers.
The guys that said they were experts on OB speakers seemed blissfully unaware this was even a well known issue.
(Baffle peaking is when the sound meets from front and back and is in phase and creates a 6db boost in the sound, usually between say 200-400 hz or thereabouts)

There is also a cancellation frequency where sound from front to back cancel each other out and result in a reduction of most all bass, as frequency goes lower and lower.
Most make up for this with Drivers with a VERY high Q factor, that partially boost bass at least at the mid and upper bass frequencies.

I recently built an open baffle setup. My reasoning was that it was about the easiest thing I could make with limited access to shop tools, and the cancellation to the sides I thought might be beneficial. Yes, the baffle peaking is a real issue, and I'm still scratching my head about how to properly measure and equalize the speaker. For now I'm just equalizing the driver response to close to flat when measured on-axis at 1 meter. If I go off axis I get surprisingly flat response about 45 degrees above the driver with no eq, but not below or to the sides, where the response is more similar to the on-axis. I think I've got it pretty good because if I go back to the listening position and measure the overall response in the room it's matching the Harman target pretty closely. Overall it sounds very good, easily besting some smaller bookshelf speakers with smaller and less efficient drivers. But that's hardly a fair comparison. With some absorber panels behind it can sound quite good at just 2 feet from the back wall. I've been very much enjoying music and movies with it so far. To know for sure how good or bad it is I'd need to build a closed box arrangement around the same or similar performing drivers and see if I can do any better.

 

[atmasphere]

I recently built an open baffle setup. My reasoning was that it was about the easiest thing I could make with limited access to shop tools, and the cancellation to the sides I thought might be beneficial. Yes, the baffle peaking is a real issue, and I'm still scratching my head about how to properly measure and equalize the speaker. For now I'm just equalizing the driver response to close to flat when measured on-axis at 1 meter. If I go off axis I get surprisingly flat response about 45 degrees above the driver with no eq, but not below or to the sides, where the response is more similar to the on-axis. I think I've got it pretty good because if I go back to the listening position and measure the overall response in the room it's matching the Harman target pretty closely. Overall it sounds very good, easily besting some smaller bookshelf speakers with smaller and less efficient drivers. But that's hardly a fair comparison. With some absorber panels behind it can sound quite good at just 2 feet from the back wall. I've been very much enjoying music and movies with it so far. To know for sure how good or bad it is I'd need to build a closed box arrangement around the same or similar performing drivers and see if I can do any better.

You can mess with 'wings' on the side and top of the baffle. Too deep and you get a cavity well resonance but they have the advantage of being twice as effective as the flat area of a baffle in terms of LF cutoff. So you can use them as a 'stand' to hold the baffle up. There are some very successful OB designs that are also multi-driver.

 

[Tim Link]

You can mess with 'wings' on the side and top of the baffle. Too deep and you get a cavity well resonance but they have the advantage of being twice as effective as the flat area of a baffle in terms of LF cutoff. So you can use them as a 'stand' to hold the baffle up. There are some very successful OB designs that are also multi-driver.

My baffle has legs to hold it up. I intentionally made it a fairly minimal sized baffle to maximize the cancelation to the sides and up and down. I'm thinking it may be a little too tight sounding in that regard so I will try extending the baffle invarious ways. For now I've removed the absorber panels I had behind the baffles. That seems to have livened the sound as expected and I think I like it better. One strange thing about my current setup is that the louder I turn it up the tigher and cleaner it seems to be, which is the opposite of the normal situation I've encountered where there's some maximum level where the room seems to get out of control. With no apparent cap on maximum volume I've been experimenting with turning it way up, which works great for some stuff. Listened to Mariah Carey's Music Box CD which is super hard hitting and great sounding at high volume. Interestingly the CD streamed to the computer from the CD player via Toslink is considerably louder than the same album streamed from Apple or Spotify. Mariah Carey's not my normal fare but the CD is here and I have to admit it's impressive. Listening now to Ali Farka "The Source", which is more my kind of thing and this sounds really nice at lower volume, 20 dB lower now that I look!

 

[JaapD]

Many loudspeakers require a form of damping, coming from the air mass inside a cabinet. Because of this I expect many Open Baffle designs to have a lousy impulse response (unless you'll have a very specifically designed OB woofer of course). You can't read this from a frequency plot. Maybe this form of distortion is appreciable by some.

Cheers,
JaapD.

 

[Tim Link]

Many loudspeakers require a form of damping, coming from the air mass inside a cabinet. Because of this I expect many Open Baffle designs to have a lousy impulse response (unless you'll have a very specifically designed OB woofer of course). You can't read this from a frequency plot. Maybe this form of distortion is appreciable by some.

Cheers,
JaapD.

That should only matter down in the bass where the back pressure starts to affect the cone motion. If you port load then it goes nuts below the resonant frequency of the port so that's still a problem if you don't cut it off soon enough. I'm crossing over at 220Hz, so pretty much avoiding the entire bass range for the open baffle. I tried taking it down to 100Hz, which measured very good in terms of response, low distortion, and room clarity. However it wasn't sounding good. The 10" drivers I'm using can really sing in the mids between 220 and 1100 Hz if they're freed up of bass duty. I'm trying 300Hz now and I think that's even better. The more I can hand over to my 18" horn loaded woofers, the more headroom I get.

 

[Anton D]

Many loudspeakers require a form of damping, coming from the air mass inside a cabinet. Because of this I expect many Open Baffle designs to have a lousy impulse response (unless you'll have a very specifically designed OB woofer of course). You can't read this from a frequency plot. Maybe this form of distortion is appreciable by some.

Cheers,
JaapD.

This all gets complicated!

This woofer thread has people who are reasonable saying impulse response in a woofer is not a thing.

I agree with your take, but it was pointed out we might be wrong, not sure!

How Deep Must the Bass Be?

I'm interested in people's opinions about how low the lowest frequency a subwoofer/woofer can produce with "acceptably low" distortion should be. I'm interested only in the lowest frequency that can be heard, not just felt, regardless of how high the spl level needs to be for that to happen. I...

www.audiosciencereview.com

 

[MarnixM]

Can such loudspeakers be successfully integrated with subwoofers? If yes, should the subwoofers also be Open Baffle or not necessarily?

I combined my Maggies (in fact bipolar “open baffles”) with a down firing, closed sub with a long stroke subwoofer (SB-acoustics). The feet of this subwoofer are 5cm high, so there is sufficient “space” for the low frequencies to radiate in all directions. Take good care placing the combination not to close to backwalls and not in room corners. Took some time and efforts to find to optimum spots. Working with an active X-over and bi-amping at X-over point of 160Hz.

 

[bob johnson]

Been in this business since the 70's Here is my simple highest value sound system for far less than most audiophile lemmings will spend on a system recipe. Source - any old laptop running Spotify premium - digital into the Mini DSP HD (with DAC) $250 for the ultimate in frequency and crossover control - with a calibrated measuring mic from your listening position to set your room up $90 - and REW for measurements - to a Bi-Amp set up, ( use what you have lying around as just about anything will do but separating the high current and low current amps does help - 1 or 2 15" woofers $80-150 each in a H or W open baffle frame cabinet. Beston ribbon with the back open $50 , full size AMT as the alternate $160. and any decent full / midrange $50 Add it up.... surprise.... Kind of emulates the Orion or LX 521 concept for much less. Thats it - code cracked for maximum value creation. Nothing beats the uncolored speed of an open baffle bass driver. Think about how they mounted Altec 604's in movie theaters.

 

[Flaesh]

Mini DSP HD (with DAC) $250

This is 4 channels. Passive crossover for MF\HF?

 

[StigErik]

Many loudspeakers require a form of damping, coming from the air mass inside a cabinet. Because of this I expect many Open Baffle designs to have a lousy impulse response (unless you'll have a very specifically designed OB woofer of course). You can't read this from a frequency plot. Maybe this form of distortion is appreciable by some.

Cheers,
JaapD.

Impulse response is ruled by the total Q, or damping factor called Qts

The damping of a dynamic loudspeaker driver is composed of two things:
A) Electrical damping by the voice coil/magnet system - Qes
B) Mechanical damping by the suspension and air load - Qms

And Qts = (Qms x Qes) / (Qms + Qes)

With most loudspeakers, the electrical damping is far greater than the mechanical. Putting a driver on an open baffle will not necessarily ruin any damping at all, since most loudspeakers have a Qes value around 0,3-0,4, meaning very high damping.

 

[JaapD]

Impulse response is ruled by the total Q, or damping factor called Qts

The damping of a dynamic loudspeaker driver is composed of two things:
A) Electrical damping by the voice coil/magnet system - Qes
B) Mechanical damping by the suspension and air load - Qms

And Qts = (Qms x Qes) / (Qms + Qes)

With most loudspeakers, the electrical damping is far greater than the mechanical. Putting a driver on an open baffle will not necessarily ruin any damping at all, since most loudspeakers have a Qes value around 0,3-0,4, meaning very high damping.

Thanks for your reply to my post. Let’s first grab some reference data.

Qts (Total Q) Value with Comments:

Less than 0.4 => A speaker driver that is well suited to a ported/vented enclosure

0.4 – 0.7 => A speaker driver that is well suited to a sealed enclosure.

Above 0.7 => A speaker driver that is well suited to free-air or infinite baffle application.

With reference to the by you mentioned Qes of 0.3-0.4 and also taking into account that you’re missing the Qms from an Open Baffle design (therefore Qts will roughly be equal to Qes), according to the above data such driver will only be suited for ported/vented enclosures, not for Open Baffle designs.

In other words, starting from an Qes of 0.3-0.4, combined with a nearly non-existent Qms from an Open Baffel design, you can’t reach a required Qts of 0.7 which brings you an optimal impulse response.

In my opinion the challenge remains how to sufficiently control the resonance frequency of the speaker in an Open Baffle design. And this refers back to me mentioning ‘unless you'll have a very specifically designed OB woofer of course’.



I hope this sufficiently explains my previous post.

Cheers,

JaapD.

 

[StigErik]

Linkwitz had the opinion that drivers with Qts less than 0.5 was the better choice for open baffle.

Frequently Asked Questions

He used the Seas L26ROY with Qts 0.27 in his LX521.